Referring to FIG. 1, a prior art ultrasound system is shown. The fundamental principle of ultrasound imaging is to use acoustic waves to help image an object. The basic blocks for ultrasound imaging is the use of an array of piezoelectric transducers in which each transducer will require a high voltage transmitter block, a transmit/receive switch block, and a low noise receiver block. Within the block Logic Control and Signal Processing block, the logic control portion determines the outcome of each transmitter and the signal processing portion uses the information from the receiver to create an ultrasound image.
The drawing in FIG. 1 shows an example of a 3-level transmitter with a burst of 4-cycles of 5.0 MHz, ±75V into a piezoelectric transducer. 3-levels implies the transmitter has transistors that would pull the output to three different voltage levels: +75V, 0V, and −75V. The amplitude may be adjusted by lowering the +75V and −75V supply rails. The burst may be consisted of one cycle or more cycles depending on what particular image mode the system is in. The transmitter frequency may be adjusted from 1.0 MHz to 15 MHz. There is a transmit/receive switch which is used to protect the receiver's input against the ±75V transmit signal. The transmit signal may cause the piezoelectric transducer to vibrate thereby creating an acoustic wave. The acoustic wave may hit the object to be imaged. An acoustic echo may be bounced back into the transducer. The transducer may now convert the acoustic echo into an electric signal which is normally no greater than a few 100 millivolts. The transmit/receive switch allows the small electrical signal to pass into the receiver. The signal from the receiver may be used to help reconstruct a small part of the image. The remaining transmitters may be used in a similar fashion to help construct a complete ultrasound image of the object.
The 3-level transmitter needs to be able to drive the transducer to a positive voltage, a negative voltage and to ground. FIG. 1 shows the positive voltage as +75V and the negative voltage as −75V. A typical implementation of a discrete 3-level transmitter is shown in FIG. 2 where +HV1 is an adjustable positive supply voltage and −HV1 is an adjustable negative supply voltage.
The 3-level transmitter shown in FIG. 2 may have three logic input controls for a given 3-level transmitter: Pin, Nin, and RTZin. When the logic input Pin is high, it may turn on transistor P1 which may then pull the output to +HV1. When the logic input Nin is high, it may turn on transistor N1 which may then pull the output to −HV1. When the logic input RTZin is high, it may turn on both transistors P2 and N2 which will then pull the output to ground. The logic input names may be better understood with the following explanation. “Pin” may be referred to as the logic input to control the output going positive. Similarly, “Nin” may be referred to as the logic input to control the output going negative. “RTZin” may be the logic input to control the output to return-to-zero. Input logic conditions where both P1 and N1 are on should be avoided as this will short the +HV1 supply voltage to the −HV1 supply voltage. Also, when P2 and N2 are on, P1 and N1 should be kept off. FIG. 3 shows an example of what the individual logic inputs would need to be to create a burst of four high voltage cycles on the transmitter output.
FIG. 4 shows how the transmitter outputs referenced to each other in a 128 channel system may look like. Each transmitter output may have a certain amount of delay time. System designers may require the flexibility to adjust the individual delay times, the output frequency, the waveform, and the number of cycles. Individual controls on when the output goes positive, negative, and ground are therefore needed. This allows them to optimize the output pattern to obtain the best possible image. Discrete and integrated transmitters today would have at least two or three input controls per transmitter. For a system requiring 128 transmitters the number of control logic pins for the transmitters would be 128 times two which is 256 control lines or times three which is 384 control lines. The controller may be one or more FPGA's with very large I/O capability or one or more custom ICs with very large I/O capability. The large number of connections causes PC board layout issues, PC board space issues, higher cost FPGA's, and reliability concerns. For systems requiring larger number of transmitters, the number of control lines will grow proportionally. The situation will obviously become worst for portable applications where board space becomes a premium. In an ultrasound system, the need for an integrated transmitter that can significantly reduces the number of logic input connections but still allows system designers the flexibility to optimize the output patterns is therefore warranted.
Therefore, it would be desirable to provide a system and method that overcomes the above.